Enough highly enriched U.S. uranium to make about 20 nuclear weapons was sneaked back to the United States from Japan over a 12-year period until last summer in a secret operation aimed at keeping it out of terrorists' hands, a senior U.S. official and Japanese specialists recently revealed.
The uranium, which was provided to Japan by the United States to build five nuclear nuclear research reactors, totaled more than 500 kg.
Details of the special repatriation operations, initiated by the U.S. National Nuclear Security Administration, a special wing of the Energy Department, have been kept under wraps for more than a decade for security reasons. The shipments began in 1996.